MINOR: version: mention that it's stable now

This version will be maintained up to around Q1 2024. The INSTALL file
also mentions it.
diff --git a/INSTALL b/INSTALL
index 9269051..1a90311 100644
--- a/INSTALL
+++ b/INSTALL
@@ -1,14 +1,14 @@
 Installation instructions for HAProxy
 =====================================
 
-This is a development version, so it is expected to break from time to time,
-to add and remove features without prior notification and it should not be used
-in production, unless you're an experienced user and are willing to follow
-weekly updates. If you are not used to build from sources or if you are not
-used to follow updates then it is recommended that instead you use the packages
-provided by your software vendor or Linux distribution. Most of them are taking
-this task seriously and are doing a good job at backporting important fixes. If
-for any reason you'd prefer to use a different version than the one packaged
+HAProxy 2.7 is a stable version, which means that it will get fixes for bugs as
+they are discovered till around Q1 2024 and should not receive new features.
+This version is mostly suited at experienced users who are willing to quickly
+follow updates. New users are encouraged to use long term supported versions
+such as the ones provided by their software vendor or Linux distribution, as
+such versions require far less common updates.
+
+If for any reason you'd prefer to use a different version than the one packaged
 for your system, you want to be certain to have all the fixes or to get some
 commercial support, other choices are available at http://www.haproxy.com/.